Field of the Invention
The invention relates to a device for triggering an airbag device accommodated in a steering wheel. The device contains a gas generator for inflating an airbag, a firing cap for firing the gas generator and an optical waveguide that is connected to a light source remote form the steering wheel and has the purpose of supplying the firing cap with a light pulse which fires the firing cap.
A device of the generic type is known from the German Patent DE 196 33 409 C1. The optical waveguide, for example a glass fiber, is optically connected to the firing cap in such a way that the firing cap is directly fired by light pulses with a sufficient energy content, whereas light pulses with a smaller energy content are used as test pulses which can be reflected using suitable devices and used to check the optical waveguide. The aforesaid patent does not contain any details on the connection of the optical waveguide to the firing cap. This connection is generally of rigid construction, which leads to increased constructional complexity in an airbag device which is accommodated in a steering wheel and rotates with the steering wheel because such optical waveguides can in themselves only be twisted to a small degree.
It is accordingly an object of the invention to provide a device for triggering an airbag device that is accommodated in a steering wheel which overcomes the above-mentioned disadvantages of the prior art devices of this general type, which has a simple structure with a high degree of functional reliability.
With the foregoing and other objects in view there is provided, in accordance with the invention, a device for triggering an airbag device accommodated in a steering wheel assembly having a steering wheel. The device contains a gas generator for inflating an airbag, a firing cap for firing the gas generator, a light source, and a coupling device having an optical waveguide connected to the light source remote from the steering wheel. The light source supplies the firing cap with a light pulse for firing the firing cap. The coupling device is disposed at least approximately concentrically with respect to an axis of rotation of the steering wheel. The coupling device is disposed between the airbag and the light source, and the coupling device configured such that the optical waveguide is isolated from a rotation of the steering wheel and ensures a functional connection of the optical waveguide to the firing cap.
According to the invention, the optical waveguide via which the light pulses for firing the firing cap are fed in from a light source is decoupled from the steering wheel in terms of rotation of the steering wheel so that the optical waveguide is not torsionally loaded. The coupling device, via which the rotational decoupling and the functional coupling are effected in the transmission path from the optical waveguide via the firing cap to the gas generator and from there to the airbag, is disposed concentrically or coaxially with respect to the axis of rotation of the steering wheel so that the function is ensured irrespective of the rotary position of the steering wheel.
In accordance with an added feature of the invention, the optical waveguide is a two-piece waveguide with an end part to be fixed to the steering wheel and ends at the firing cap, and a feed part starting from the light source. The feed part is isolated from the steering wheel in terms of its rotatability. The feed part has a first light exit window and the end part has a second light entry window disposed opposite the first light exit window of the feed part coaxially with the axis of rotation of the steering wheel.
In accordance with an additional feature of the invention, the decoupling device includes a bearing to be attached to a steering column of the steering wheel. The feed part has a steering-wheel end accommodated in the bearing and the steering column is connected fixed in terms of rotation to the steering wheel.
In accordance with another feature of the invention, the gas generator is to be connected fixed in terms of rotation to the steering wheel and is rotatable in relation to the firing cap, and the firing cap is provided coaxially to the axis of rotation of the steering wheel and is decoupled from the steering wheel in terms of rotation.
In accordance with a further feature of the invention, the gas generator has a recess formed therein and the firing cap is accommodated in the recess. The decoupling device has a bearing disposed between the gas generator and the firing cap.
In accordance with another added feature of the invention, the firing cap is connected fixed in terms of rotation to the steering wheel and is rotatable in relation to an end of the optical waveguide facing the firing cap.
In accordance with another additional feature of the invention, the firing cap has a housing with a through-opening formed therein, and the optical waveguide is accommodated in the through-opening in the housing of the firing cap. The decoupling device has a bearing disposed in the housing and the optical waveguide has an end part accommodated in the bearing.
In accordance with another further feature of the invention, the end part of the optical waveguide has a light exit window, and a fluorescent film is disposed between the light exit window of the optical waveguide and the firing cap.
In accordance with a concomitant feature of the invention, the steering wheel assembly has a steering column connected fixed in terms of rotation to the steering wheel. The decoupling device has a bridging tube to be disposed in the steering column and rigidly connected to a wall of the steering wheel assembly. The optical waveguide is guided from an exterior space through the bridging tube into an interior of the steering column. The decoupling device has a bearing disposed between the bridging tube and the steering column.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a device for triggering an airbag device which is accommodated in a steering wheel, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.